Primer assembly



Sept. 28, 1943. H, L. M AT ELT AL" PRIMER 'ASSEMBLY INVENTORS- TURNER.

l M A: j T I U r I 1 HARRY L. MOAT.

. a H a: mum

R E ILv X 0 R T D L U A P Patented Sept. 28, 1943 PRIMER ASSEMBLY Harry L.

Moat, Wilmington, DeL, and Paul D.

Troxler, Mahopac, N. Y., assignors to Atlas Powder Company, Wilmington, Del., a corporation of Delaware Application November 2, 1939, Serial No. 302,478

9 Claims.

In blasting with explosives it is necessary to prime at least one of the explosive cartridges with an explosion initiator such as a detonator. This invention relates to a pre-formed primer assembly containing an electric, explosion initiator and adapted to be readily combined with a cartridge of explosive to form a primed cartridge.

In blasting operations, particularly in underground work, it has been found that considerable saving in time and labor can be accomplished by preparing the primed cartridges at a point considerably removed from the face of the work, as for example at the entrance to the tunnel or shaft leading to the place where boring and loading is being conducted. In addition to the saving in time and labor, such procedure frequently enables the more careful preparation of the primed cartridges in those cases where the preparation of the primed cartridges at the face of the work would have to be conducted under confusing conditions existing as a result of drilling,

removal of debris, etc., which frequently involves the use of fairly heavy and noisy machinery.

Conventional priming of explosive cartridges however involves the puncturing or slitting of the wrapper of the dynamite or other explosive cartridge employed and the insertion and fastening of the explosion initiator thereto. The accidental firing of such a primed cartridge would of course be highly disastrous and it has been generally customary to prohibit the carrying of such primed cartridges for any considerable distance through mines or tunnels. Thus to a large extent the advantages which could be accomplished by priming cartridges at a point removed from the over-crowded conditions frequently occurring at the borehole have been denied.

An object of the present invention is the provision of a primer assembly which may be readily assembled with a cartridge of explosive at the borehole.

Another object of the present invention is the provision of a primer assembly which is free of explosive ingredients other than the explosion initiator and which may be carried through shafts or tunnels to the location of the blasting operations.

A still further object of the invention is the provision of a primed cartridge which insures the firing of the cartridges of explosive located in the borehole without the necessity of following the conventional practice of puncturing a cartridge of explosive and inserting and securely tying the explosion initiator thereto.

Other objects of the invention will hereinafter more fully appear.

In the drawing, Fig. 1 is a longitudinal view, partly in section, of a primer assembly of the present invention; Fig. la. is a sectional view on line H of Fig. 1; Fig. 2 is a longitudinal view, partly in section, of the primer assembly combined with a cartridge of explosive; Fig. 3 is a similar view of a modification of the primer. assembly of the present invention; Fig. 3b is a sectional view on line b'b of Fig. 3; Fig. 4 is a bottom end view of a plug constituting another modification of the primer assembly; and Fig. 5 is a sectional view of another type plug employed in the primer assembly'of the present invention.

Referring to Figs. 1 and 1a, l represents a shell having one end open at 2 and the other end closed as by folding over the end of the shell at 3. This shell may be a conventional dynamite wrapper having one end left open but is preferably made of a slightly larger diameter than the conventional explosive cartridge to be combined therewith for reasons that will presently ap- Located in the lower end of the shell and abutting the closed end of the shell is a plug generally indicated by 4, said plug having a hole 5 extending longitudinally therethrough for thereception of an explosion initiator 6, diagrammatically indicated as a delay electric blasting cap. It is to be understood that the explosion initiator may be any other form of electric firing device as a non-delay blasting cap or an electric squib. The plug 4 is made of non-explosive material, preferably of substantial strength and rigidity such as wood. Instead .of wood, a roll of corrugated paper 4' or other non-explosive collapse-resistant material may be employed as will be readily apparent to those skilled in theart.

The explosion initiator 6 is inserted into the hole 5 so that the firing or business end faces upwardly toward the open end 2 of the shell I. When corrugated paper is employed, it may be rolled as shown in Fig. 5. As shown in Fig. 1, the plug 4 is preferably of a length equal to the length of the explosive initiator 6 so that the .plug covers the entire length of the said initiator.

From the lower end of the explosion initiator the lead wires 1 are brought around the bottom end of the plug and upwardly along the side thereof, this portion of the lead wires lying be-' tween the plug and the shell I. If so desired, the plug may be grooved as indicated by 20 and 20' in Fig. 4 along its bottom and side wall for the reception of this portion of the lead wires. Prior to assembly with an explosive cartridge the remaining length of the lead wires is conveniently bundled in the upper, otherwise empty, end of the shell I as indicated at I.

The plug 4 and the bundle of lead wires I may be sufiiciently tight fitting in the shell I so that no other fastening means is required to keep the plug and explosion initiator from falling out of the shell. It is to be understood, however, that the plug 6 may be glued or otherwise fastened to the shell as by stapling. Where staples such as, for example, those designated by I9 and I9 in Fig. 1 are employed they may conveniently be inserted through the shell into the plug 4 around the lead wires to thereby hold the lead wires as well as the shell to the plug.

If so desired, a portion of the lead wires may extend out of the open end 2 and bear an identiiying tag I8 having printed thereon the type of explosive initiator contained in the assembly. This extension of the lead wires and the tag I8 can be easily gripped to pull the bundle of lead wires 1' out of the shell i when the assembly is to be combined with an explosive cartridge in the manner hereinafter set forth. It is to be understood, however, this extension of the lead wires and the tag I8 may be eliminated if so desired, as the bundle 1' may be shaken or otherwise removed from shell 2 and the identification of the type of explosive initiator can be shown elsewhere as for example on the outside of shell I.

When it is desired to prepare a primed explosive cartridge from the primer assembly above described, it is merely necessary to pull the bundle of lead wires I out of the upper end of the shell and insert therein a cartridge of explosive indicated as 8 in Fig. 2. Preferably the explosive cartridge employed is a cut cartridge, that is, a cartridge which has been cut through so that the explosive is exposed at one end, and the end with the explosive so exposed is inserted into the shell I so that the explosive is directly adjacent the firing end of the initiator 6. By having the shell I of only slightly larger diameter than that of the explosive cartridge 8 the explosive cartridge is held securely in place by a frictional engagement, or the explosive cartridge may be fastened in the priming tube by any suitable means such as a pin indicated as 2i in Fig. 2. It can be seen that where the cartridge of explosive is pressed down firmly against the upper end of the plug 4, the firing or business end of the explosion initiator is adjacent to and correctly pointed toward the explosive cartridge with no opportunity for slippage or displacement in a manner to decrease its detonating efficiency or to cause a failure. Furthermore, the abutting ends of the cartridge 8 and the plug 4 are covered by the shell I so that there is no opportunity for the gathering of drilling refuse between the explosive cartridge and the explosion initiator when the primed cartridge is shoved into the borehole.

While We have shown the plug 4 and the explosion initiator 6 as of about equal length so that the explosion initiator is covered throughout its entire length, it is to be understood that the plug may be shorter than the explosion initiator in which case the firing or business" end of the initiator would extend upwardly beyond the end of the plug 4. With this latter modification the firing end of the initiator will puncture and extend into the cartridge 8 when the latter is shoved down into the shell I and upon the plug 4.

The modification shown in Figs. 3 and 3a is of this latter type. In this embodiment shell 9 has inserted at one end a wooden plug in having an opening II for the reception of the electric, explosion initiator l2. Plug II is rounded at its outer end I3 and is provided with a shoulder I4 abutting the end of the shell 9. This rounded end of the plug protects the cartridge as it is shoved down the borehole and also tends to prevent the assembly from becoming jammed against irregularities in the borehole.

Plug I 0 is grooved as indicated at I5 and the lead wires I6 extend through the groove and between the shell and the plug into the opposite end of the shell wherein they are bundled as indicated at II. By having that portion of the groove I5, which lies in the rounded end of the plug, relatively deep, the wires passing therethrough are substantially protected even though they are not completely covered as by 3 in the embodiment shown in Fig. 1.- A portion of the lead wires may extend out of the open end of the shell and bear a tag I8 for the purposes explained above with respect to the lead wire extension and tag I8 of Fig. 1.

In the modification shown in Fig. 3 the plug I0 is shorter than the initiator I2 so that when the bundle of wires is removed and a cartridge of explosive inserted in the shell and pushed down upon plug I0, the firing or business end of the explosion initiator will puncture and extend into the explosive cartridge, or the explosive cartridge may be previously punctured to accommodate the initiator. It is to be understood that in the modification shown in Fig. 3, the plug I0 may be of suflicient length to cover the full length of the initiator if so desired. The plug I0 may also be stapled, glued or otherwise fastened to the shell 9 as described above with reference to the assembly of Fig. 1.

In blasting work where a plurality of explosive cartridges are employed in each borehole, we preferably place the primed cartridge of the present invention in the bottom of the borehole with the initiator at the bottom of the charge. The plug and initiator are securely held in proper position as is that portion of the lead wires leading outwardly from the shell but between said shell and the plug and explosive cartridge. We find it highly advantageous in loading the borehole, particularly where the initiator is seated on the bottom facing upwardly, to have that portion of the lead wires which extends upwardly along the side of the primed cartridge, protected and held in place by the shell, as otherwise the primer must be loaded into the borehole with great care in order to prevent abrasion of the lead wires and displacement of the initiator from its proper position. A further advantage is that in case of a misfire the primer assembly will generally remain intact as a unit, particularly where it is fastened together bygluing or stapling. is thus more easily retrieved as a whole from the muck of the borehole.

With the primed cartridge located at the bottom of the borehole the explosive cartridge or cartridges thereabove cushion any tamping action and help protect the more sensitive detonator. Of course it is to be understood that the invention is not to be limited in this respect as the primer of the present invention may be located in any position in the borehole if so desired.

Thus, it may be placed with one or more unprimed explosive cartridges above and below it or it may be placed at the upper end of the borehole with the initiator facing downwardly if so desired.

The terms electric, explosion initiator as used herein are meant to include all types of electric firing devices, as for example electric blasting caps, delay electric blasting caps and electric squibs.

Having described our invention, what we claim is as follows:

1. A primer assembly adapted to be associated with an explosive charge comprising a tubular member adapted to receive and retain in one end thereof an explosive cartridge, a non-explosive collapse-resistant plug disposed in the opposite end of said tubular member and adapted to serve as an abutment for the explosive cartridge to be received in the tubular member, said plug having a longitudinal opening therein, an electric explosion initiator positioned in said opening and having its lead wire extending from a point adjacent the plugged terminus of the tubular member into the portion of said tubular member intended to receive said explosive cartridge, said primer assembly being free of explosive other than the explosion initiator.

2. A primer assembly as set forth in claim 1 and wherein the lead wire is bundled into the charge-receptive portion of said tubular member.

3. A primer assembly adapted to be associated with an explosive charge comprising a tubular member having at least one end closed and adapted to receive and retain in the open end thereof an explosive cartridge, a non-explosive collapse-resistant plug disposed in the opposite end of said tubular member and adapted to serve as an abutment for the explosive cartridge to be received in the tubular member, said plug having a longitudinal opening therethrough, an electric explosion initiator in said opening and positioned. with its firing end directed toward the far end of the tubular member and with its lead wire end adjacent the closed end of the tubular member, the lead wire from said initiator extending from a point adjacent the plugged terminu of the tubular member into the portion of said tubular member intended to receive said explosive cartridge, said primer assembly being free of explosive other than the explosion initiator.

4. A primer assembly as set forth in claim 3 and wherein the lead wire is bundled into the charge-receptive portion of said tubular member and covers the firing end of the initiator.

5. A primary assembly adapted to be associated with an explosive charge comprising a tubular member having one end open and the other end closed and adapted to receive and retain in the open end thereof an explosive cartridge, 9. nonexplosive collapse-resistant plug disposed in the opposite end of said tubular member and adapted to serve as an abutment for the'explosive cartridge to be received in thetubular member, said plug having a longitudinal opening therein, an electric explosion initiator longitudinally posi- 5 tioned in said opening with its firing end directed toward the open end of the tubular member and with its lead wire end adjacent the closed end of the tubular member, said plug; being of sumcient length to substantially cover and protect the sidewalls of the initiator, the'lead wire from said initiator extending from a point adjacent the plugged terminus of the tubular member into the portion of said tubular member intended to receive said explosive cartridge, said primer assembly being free of explosive other than the explosion initiator.

6. A primer assembly as set forth in claim 5 and wherein the lead wire is bundled into the charge-receptive portion of said tubular member and covers the firing end of the initiator.

'7. A primer assembly adapted to be associated with an explosive charge comprising a tubular member having at least one end closed and adapted to receive and retain in the open end thereof an explosive cartridge, an electric explosion initiator positioned within said tubular member and adjacent a closed end of the tubular member, said initiator being supported and positioned therein by non-explosive collapse-resistant material so that the firing end of the initiator is directed toward the far end of the tubular member, and a lead wire extending from said initiator substantially wholly within said tubular member Where it is bundled into the charge receptive portion of the tubular member, said primer assembly being free of explosive other than the explosion initiator.

8. A primer assembly adapted to be associated with an explosive charge comprising a tubular member adapted toreceive and retain in one end thereof an explosive cartridge, a non-explosive collapse-resistant plug disposed in the opposite end of said tubular member and adapted to serve as an abutment for the explosive cartridge to be received in the tubular member, said plug having a longitudinal opening therein, an electric explosion initiator positioned in said opening and having its lead wire extending substantially wholly within said tubular member from a point adjacent the plugged terminus of the tubular member into the portion of said tubular member intended to receive said high explosive cartridge, said lead wire being bundled into the charge-receptive portion of said tubular member, and a grip on said bundle of wire so placed that it may be seized to pull the bundle of wire out of the tubular member.

9. A'primer assembly as set forth in claim 8 and wherein the grip comprises an extension of the wires and an identification tag.

HARRY L. MOAT. PAUL D. TROXLER. 

